1. Field of the Invention
The present invention relates to an apparatus for controlling a network access of an asynchronous transfer mode (ATM) host adapter and more particularly to an host adapting apparatus which can be applied to an ATM apparatus connected to a small scale shared media type ATM network as well as a general ATM host apparatus.
2. Discussion of Related Art
According to structure of an existing ATM adapter, access of shared media is not considered. A general ATM adapter structure is divided as follows.
First, there are two methods in packet segmentation. One is storing transmit packet data in a host memory, and the other is storing the transmit packet data in a local memory of an adapter. While the former method has an advantage of greatly reducing a size of the adapter""s local memory, it has a drawback of decreasing efficiency of a system bus due to access to the system bus in the units of cells. The latter method increases the efficiency of the system bus by accessing the system bus in the units of packets, but it has a drawback of requiring a large size of the local memory.
Second, when using the host memory, the packet data in the host memory is segmented in the units of cells and then stored in the shared local memory, or the packet data is stored in a dedicated small size buffer within the adapter and then transmitted to a physical link.
In the former case, since access to a local bus is performed in the units of cells, there is a drawback of increasing contention of the local bus.
Third, there are two methods in packet assembly. One is storing cells received from the physical link in the shared local memory, and the other is storing the cells in the dedicated small size buffer within the adapter. When the cells are transmitted from the physical link, since there are various bursts, a very large buffer is required. So the lather method is more efficient than the former.
Accordingly, the present invention is directed to an ATM host adapter apparatus with ability of shared media access that substantially obviates one or more of the limitations and disadvantages of the related art.
An object of the present invention is to provide an ATM host adapting apparatus for preventing damage in traffic flow properties over shared media by instantaneously adding cells every predetermined period in an ATM host, and allowing the ATM host to access a home area or small business area ATM access network having single ring topology.
Additional features and advantages of the invention will be set forth in the description which follows, and in part will be apparent from the description, or may be learned by practice of the invention. The objectives and other advantages of the invention will be realized and attained by the structure as illustrated in the written description and claims hereof, as well as the appended drawings.
To achieve these and other advantages, and in accordance with the purpose of the present invention as embodied and broadly described, an ATM host adapter apparatus includes: a storage block(local memory) for storing packet information, received cells, and parameters; an ATM network interface handling block for performing direct memory access(DMA) of ATM cells and parameter stored therein, segmenting transmit packet information, reassembling received cells, transmitting and receiving the ATM cells to physical shared media, and arbitrating in the direct memory access; and a local bus for connecting the storage block to the ATM network interface handling block.
The present invention provides structure of shared medium access, segmentation, and reassembly which should be provided by an ATM host adapter when ATM hosts in a small home area ATM network or a small business area ATM network communicate with each other through shared media of single ring topology.
When the ATM host has cells to transmit, the ATM host adapter cyclically transmits the cells to the shared media. The ATM host adapter uses a host memory as a buffer for packets to be segmented. The cells in the host memory are segmented by the ATM host adapter and temporarily stored in a segmentation buffer within the ATM host adapter before being transmitted to a physical link. The cells received from the shared media are classified into drop cells, copy cells, and relay cells so as to be appropriately processed.
The drop cells are temporarily stored in a local memory. Only on valid ATM connection cells are classified and reassembled using the host memory. The relay cells are temporarily stored in a relay buffer within the ATM host adapter and preferentially transmitted to the shared media. When the copy cells are received, the cells are copied within the ATM host adapter and simultaneously transmitted to both the local memory and the relay buffer. The copy cells each is treated with the same process as applied to the drop cells and relay cells.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory and are intended to provide further explanation of the invention as claimed.